Trigger mechanism for use with automatic firearms

ABSTRACT

1,045,126. Trigger mechanisms. STERLING ENGINEERING CO. Ltd. May 7, 1965, No. 19383/65. Heading F3C. The trigger mechanism of Specification 834,835 is modified by pivotally mounting the sear 5 on a link 27 pivoted at 28 so as to permit the sear to move longitudinally or substantially longitudinally. The link 27 may be reversed from the position shown in which the abutment 14 may engage the face 18 to prevent the sear from moving longitudinally, the firearm firing automatically, to a position in which the abutment 14 cannot engage the face 18, the firearm being then only capable of firing single shots.

19, 1 E. RUFFELL 3,

TRIGGER MECHANISM FOR USE WITH AUTOMATIC FIREARMS Filed April 29, 1966 (I 1 f O I 4 Mm N United States Patent 3,358,560 TRIGGER MECHANISM FOR USE WITH AUTGMATIC FIREARMS Leslie Ernest Rutiell, Dagenham, England, assignor to Sterling Engineering Company, Limited, Dagenham, England Filed Apr. 29, 1966, Ser. No. 546,221 Claims priority, application Great Britain, May 7, 1965, 19,333/65 4 Claims. (Cl. 89-142) ABSTRACT OF THE DISCLOSURE A trigger mechanism for an automatic firearm, having a trigger, a sear and a sear pivoting link member which pivots to allow movement of the sear substantially longitudinally of the firearm without a sliding guide element being required.

The invention relates to trigger mechanisms for automatic firearms.

In trigger mechanisms for automatic firearms, firing may be controlled by a pivoted sear movable by the operation of a trigger. The sear can also be capable of longitudinal movement, by means of a pin and slot coupling, which enables the sear to be decoupled from the trigger, in a position in which firing is prevented, the sear arresting the bolt after recoil.

In some conditions, foreign matter, such as particles of sand or mud, may become lodged in the slot of such a mechanism and inhibit the longitudinal movement of the sear. The mechanism includes a device by which the weapon can be set to fire either continuously or one round at a time, and if this fault occurs during the second setting, the sear will not move to the rear when the bolt is released on firing, but will remain engaged with the trigger. Thus, as long as the trigger is held the weapon will continue to fire, as if set to operate in the first manner.

The object of this invention is therefore to provide an improved trigger mechanism for an automatic firearm in which the sear is capable of longitudinal as well as pivotal movement.

It is a further object of the invention to provide a trigger mechanism for an automatic firearm, the mechanism including a pivotal sear movable by operation of a spring-loaded trigger, and a link pivoted to the sear for constraining the sear into a path extending substantially longitudinally of the firearm.

It is a further object of the invention to provide a trigger mechanism for an automatic firearm, the mechanism comprising a pivotal sear, in which the sear is rotatably coupled to a link which is pivotal about a fulcrum displaced from the coupling point whereby the sear is capable of substantially longitudinal movement.

Movement of the sear can be controlled by a selector device which can be positioned at will to provide a safe and two firing condition, and in one of the firing conditions the selector device acts upon the link to preclude pivotal movement thereof about the fulcrum.

By way of example, a trigger mechanism embodying the invention and including a selector device is described below with reference to the accompanying drawings, in which:

FIGURE 1 is a side view, partly in section, of the trigger mechanism, the selector device being shown in a first position;

FIGURE 2 is a like view of the mechanism with the selector device in a second position; and

FIGURE 3 is a similar view of the mechanism with the selector device in a third position.

The trigger mechanism shown in the drawings com- 3,358,565 Patented Dec. 19, I967 prises a trigger 2 pivotally mounted on a trigger frame 1, the trigger having a step 3 at its rear upper end for engaging a complementary step 4 on a sear 5. The sear 5 is mounted for pivotal movement about a pivot rod 6 and a link 27 is rotatably coupled to the sear by being also pivotally mounted on the rod 6. The link 27 can also pivot about a fulcrum provided by a further pivot rod 28 on the frame 1 at a position displaced from the pivot rod 6. It will be evident that pivotal movement of the link 27 about the pivot rod 28 through a small angle causes the upper end of the link coupled to the sear 5 to perform an arcuate movement about the axis of rod 28. Thus, the sear itself is moved substantially longitudinally of the firearm when the trigger frame 1 is fitted thereto.

Both the trigger 2 and sear 5 are acted on by a compression spring 8 housed in an inclined bore in the sear. The spring 8 acts directly on the sear 5 and acts on the trigger 2 by means of a plunger 9 slidably received in the bore. A second compression spring 10 is coiled about a guide rod 11 which extends from a pivot pin 12 at the rearmost part of the sear 5 to a pivotal point 13 on the frame 1.

The trigger mechanism also includes a selector device comprising an abutment 14 rotatable by an external selector lever (not shown) about a pivot rod 15 on the frame 1. The abutment 14 can be held in any one of three positions by means of a resilient catch device comprising a pair of ball bearings 24 held by but partially projecting through, apertures on opposite sides of the abutment 14 the balls being urged apart by a spring between them so as to engage in any one of three pairs of recesses 25 in the frame 1 which serve as detents. A stop 26 is provided on the frame 1 to limit rotation of the abutment 14 in the anticlockwise direction. Any other suitable locating device for the abutment 14 can of course be employed instead.

In the position of the abutment 14 shown in FIGURE 1, the abutment can engage a face 17 on the bottom of the sear towards the rear thereof. In the position shown in FIGURE 3, the abutment 14 is disposed towards a recess 19 in the bottom surface of the sear 5, forward of the face 17. In the position shown in FIGURE 2, the abutment is against the stop 26 and can engage a face 18 on the link 27.

When the abutment 14 is opposite the face 17, that is, in the position shown in FIGURE 1, the trigger mechanism is in its safe condition and the weapon cannot be fired. Thus if the bolt (not shown) is in the cocked position, that is, to the rear, an upwardly projecting part 20 of the sear 5 is engaged with the bent of the bolt which, due to the pressure of the bolt return spring, holds the sear in its most forward position. In this position the steps 3 and 4 are in engagement with each other. If pressure is applied to the trigger this causes the sear 5 to rotate about the pivot rod 6, but only to a limited extent because the face 17 comes into engagement with the abutment 14 after a small rotation, and this prevents further movement of either the sear 5 or the trigger 2. Thus the part 20 of the sear cannot be withdrawn from the bent of the bolt and firing cannot take place.

If the bolt is forward with the mechanism in the position shown in FIGURE 1, the weapon cannot of course fine even if the part 20 of the sear 5 were to be depressed by action of the trigger. Depression of this part 20 must however be prevented, or at least limited, to guard against the chance that the bolt might bounce back, as when the weapon is accidentally jarred, pick up a round, and fly forward to fire. With the bolt forward, the part 20 of the sear 5 lies in a recess in the bolt so that the sear is moved to its most rearward position by the action of the compression spring 8. This movement of the sear 5 is permitted by pivoting of the link 27 about the pivot rod 28. In this position of the sear the steps 3 and 4 are out of engagement with each other and hence pressure is applied to the trigger 2, this has no effect upon the sear, which cannot in any event be sufiiciently depressed to permit firing because engagement of the face 17 with the abutment 14 limits pivotal movement of the sear.

When the abutment 14 is in the intermediate position facing the recess 19, as shown in FIGURE 3, the weapon is in its semi-automatic position, that is, it is set to fire one round only at a time. If the weapon has been cocked, the sear 5 is held in its most forward position by pressure of the bolt and when the trigger 2 is pulled, the sear is free to rotate about the pivot rod 6 until the part 20 is withdrawn from the bent of the bolt. The bolt is thus released and firing takes place. With the release of the bolt, the forward pressure on the sear is removed and the compression spring 8 then drives the sear 5 to the rear into the position shown in FIGURE 3, by causing the link 27 to pivot about the pivot rod 28, thus disengaging the steps 3 and 4 from each other. Whilst the trigger 2 is still held, the spring 8 is under maximum compression and causes the sear 5 to rotate to a position in which it is still disconnected from the trigger but in which the part 20 lies in the path of the bolt as it flies forward after recoil. The bolt is therefore arrested in its cocked position. The bolt then exerts forward pressure on the sear 5 and the sear will move forwardly, by pivotation of the link 27 about the pivot rod 28, until the step 4 engages the step 3 on the trigger. As long as the trigger is held the sear 5 is prevented from moving to its most forward position, but when the trigger is released, movement of the sear to this most forward position will take place and the firearm will be in a condition to fire another round.

When the abutment 14 faces the face 18, as shown in FIGURE 2, the firearm is in its automatic condition. In this position, the sear 5 is held permanently in its most forward position since engagement of the abutment 14 with the face 18 of the link 27 prevents the link from pivoting on a clockwise direction. Consequently, the sear 5 cannot move rearwardly. Thus the sear 5 remains in contact with the trigger 2 and follows its every movement, so that when the trigger is pulled, the sear pivots about the pivot rod 6 and the part 20 is withdrawn from the path of the bolt and the weapon fires. As long as the trigger is held, the part 20 is kept withdrawn and the Weapon will continue to fire. When the trigger 2 is released the sear 5 will follow the movement of the trigger and pivot back to its initial position and arrest the bolt to terminate firing.

The function of the second spring is to assist the spring 8 in effecting the return movement of the sear as during this movement both ends of the spring 8 are moving which reduces its effective force.

It will be appreciated that the single link 27 can be replaced by a more complex link system, provided that at least substantially longitudinal movement of the sear 5 is permitted. Moreover, the invention could be embodied in mechanisms in which the sear is not directly engaged by the trigger. Thus the invention can be embodied in a variety of trigger mechanisms and the trigger mechanism shown in the drawings may be modified in a variety of ways within the scope of the invention as defined in the following claims.

What is claimed is:

1. A trigger mechanism for an automatic firearm, comprising a frame structure for mounting the mechanism on said firearm, a spring loaded trigger, means mounting the trigger for operating movement in the frame structure, a scar, a link member, means mounting the sear for pivotal movement at a first position on said link member, sear actuating means for causing pivotal movement of the sear upon operation of the trigger, and means at a second position on the link and mounting the link for pivotal movement in the frame structure toconstrain the sear into a path extending substantially longitudinally of the firearm and into and out of engagement with the sear actuating means.

2. A trigger mechanism for an automatic firearm comprising a frame structure, a trigger pivoted on the frame, a sear, a link pivoted at one end to the sear and at the other end to the frame and providing for substantially longitudinal movement of the sear relative to the firearm, said trigger and sear having latch faces in normal engagement, a first spring means interposed between and adapted to oppositely pivot said trigger and sear and to separate said latch. faces, a selector shiftable between three positions where it respectively engages and blocks all pivotal movement of said link, where it is out of contact with said link and sear, and where it so engages the sear that the sear is maintained in operative contact with the trigger, and a second spring means interposed between the sear and the frame for aiding sear return movement by said first spring means.

3. A trigger mechanism as claimed in claim 1 having a selector device, and means for retaining the device in either of first and second selected positions, the device engaging the link in one of the positions to restrict or preclude pivotal movement thereof, and being clear of the link in the other position to permit such pivotal movement.

4. A trigger mechanism as claimed in claim 3 having means for retaining the selector device in a third position in which the device acts to prevent pivotal movement of the sear.

References Cited UNITED STATES PATENTS 2,432,486 12/1947 Patchett 89-142 3,012,479 12/1961 Ruffell 89-142 BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

1. A TRIGGER MECHANISM FOR AN AUTOMATIC FIREARM, COMPRISING A FRAME STRUCTURE FOR MOUNTING THE MECHANISM ON SAID FIREARM, A SPRING LOADED TRIGGER, MEANS MOUNTING THE TRIGGER FOR OPERATING MOVEMENT IN THE FRAME STRUCTURE, A SEAR, A LINK MEMBER, MEANS MOUNTING THE SEAR FOR PIVOTAL MOVEMENT AT A FIRST POSITION ON SAID LINK MEMBER, SEAR ACTUATING MEANS FOR CAUSING PIVOTAL MOVEMENT OF THE SEAR UPON OPERATION OF THE TRIGGER, AND MEANS AT A SECOND POSITION ON THE LINK AND MOUNTING THE LINK FOR PIVOTAL MOVEMENT IN THE FRAME STRUCTURE TO CONSTRAIN THE SEAR INTO A PATH EXTENDING SUBSTANTIALLY LONGITUDINALLY OF THE FIREARM AND INTO AND OUT OF ENGAGEMENT WITH THE SEAR ACTUATING MEANS. 